Neumann U67 Clone : D-U67 Tube Microphone Build Thread.

[Studio Mollan]

Maybe we just need a "Bright" switch?

Cheers,
jb

I seriously consider making the inverting switchable. Or at least an internal jumper. As stated before I really don't have a problem with the 67 without the feedback circuit. A good soundig microphone either way.
/
Emil

 

[JessJackson]

So dan are you saying the complete fix would be swapping:

5 with 12
7 with 10
1 with 4

?

 

[poctop]

So dan are you saying the complete fix would be swapping:

5 with 12
7 with 10
1 with 4

?

from the top of my head yes

So audio Primary, Secondary , and then the feedback winding as well , so 3 swaps and everything will be on track.

, but i have prepared a huge mailing list with all the explanation and pad number swapping procedure that I should be able to send out once i am back home as i am travelling this week,  every customer from the very beginning will be adressed.

thanks for you wrap-up Jesse and thanks to all user for you understanding and cooperation.
Best,
Dan,

 

[Studio Mollan]

So dan are you saying the complete fix would be swapping:

5 with 12
7 with 10
1 with 4

?

from the top of my head yes

So audio Primary, Secondary , and then the feedback winding as well , so 3 swaps and everything will be on track.

, but i have prepared a huge mailing list with all the explanation and pad number swapping procedure that I should be able to send out once i am back home as i am travelling this week,  every customer from the very beginning will be adressed.

thanks for you wrap-up Jesse and thanks to all user for you understanding and cooperation.
Best,
Dan,

I just switched 5-12. You're saying that th secondary and primary needs to be reversed as well? Wouldn't that just undo the whole feedback polarity change?

 

[poctop]

So dan are you saying the complete fix would be swapping:

5 with 12
7 with 10
1 with 4

?

from the top of my head yes

So audio Primary, Secondary , and then the feedback winding as well , so 3 swaps and everything will be on track.

, but i have prepared a huge mailing list with all the explanation and pad number swapping procedure that I should be able to send out once i am back home as i am travelling this week,  every customer from the very beginning will be adressed.

thanks for you wrap-up Jesse and thanks to all user for you understanding and cooperation.
Best,
Dan,

I just switched 5-12. You're saying that th secondary and primary needs to be reversed as well? Wouldn't that just undo the whole feedback polarity change?

Since I did not have a definitive answer on this one as I asked Oliver as well  but it maybe that some interaction with the feedback winding have an interaction with the the phase of both audio winding and prevent any phase shifting issue as well if any , it may very well be that just swapping 5-12 on the mic pcb clear the de-emphasis issue , but reversing the audio in and out as well will ensure that everything will work as intented,

so the complete 100% fix is to swap the feedback , audio primary and audio secondary , you would then be the best candidate at this time to tell us that swapping the audio tap as well makes a difference or not .

Best,
DAn,

 

[micaddict]

So what does this mean for this comparison, for instance?
http://benoitlaur.com/a-b-original-neumann-u67-vs-clone-u67/
Ben did use the AMI tranny.



Henk

 

[poctop]

So what does this mean for this comparison, for instance?
http://benoitlaur.com/a-b-original-neumann-u67-vs-clone-u67/
Ben did use the AMI tranny.



Henk

I had tons of very nice comments on the mic even tough it had and feedback winding errata

just means that it will probably even sounds much better with the fix.

means also that some comparaison will remain relative for the moment beeing.

and i am very sorry for the mistake but it can be fixed very easy.

I will not miss anyone on the annoucment Promised



Ps: i am just in touch with a fellow member that has a D-U67 with a genuine K67 neumann in it and the feeback errata , i am working with him to take sample before and after the fix and have some picture done while fixing it .  eventough the first impression from this user was awesome.  i guess we might see this as an optional de-emphasis if needed or not , 

 

[dmp]

so the complete 100% fix is to swap the feedback , audio primary and audio secondary

Swapping all three windings will give you the exact same setup as not swapping any.
Swapping the feedback only, with respect to the primary, is the solution that makes sense.
Only swap the secondary (with respect to the primary) if the mic output is out of phase with the sound source - i.e. compare to a known good mic.

So what does this mean for this comparison, for instance?

If you boost +10dB @ 15kHZ on a correct u67, it would probably still sound good. It would just sound brighter.
I think this shows DIY is a learning experience!
And the jury is still out on the AMI transformer. It could be that not all the transformers are wound the same way. Some may work as original.
Best to scope out your transformer to verify how it is built.

 

[Studio Mollan]

So dan are you saying the complete fix would be swapping:

5 with 12
7 with 10
1 with 4

?

from the top of my head yes

So audio Primary, Secondary , and then the feedback winding as well , so 3 swaps and everything will be on track.

, but i have prepared a huge mailing list with all the explanation and pad number swapping procedure that I should be able to send out once i am back home as i am travelling this week,  every customer from the very beginning will be adressed.

thanks for you wrap-up Jesse and thanks to all user for you understanding and cooperation.
Best,
Dan,

I just switched 5-12. You're saying that th secondary and primary needs to be reversed as well? Wouldn't that just undo the whole feedback polarity change?

Since I did not have a definitive answer on this one as I asked Oliver as well  but it maybe that some interaction with the feedback winding have an interaction with the the phase of both audio winding and prevent any phase shifting issue as well if any , it may very well be that just swapping 5-12 on the mic pcb clear the de-emphasis issue , but reversing the audio in and out as well will ensure that everything will work as intented,

so the complete 100% fix is to swap the feedback , audio primary and audio secondary , you would then be the best candidate at this time to tell us that swapping the audio tap as well makes a difference or not .

Best,
DAn,

Ok. That sold me. I will do all the tests, as comparative as possible, but I'm under a pretty heavy work load at the moment and the studio is busy pretty much 24/7. I'll try to do it this weekend. I'd love to give something back to the forum.
/
Emil

 

[micaddict]

I ask because I really liked the D67 in Ben's shootout. In this particular case I liked it better than the original U67.
I did notice some extra air in the D67, which I reported in my reply to Ben's post. But it didn't sound as +10dB @ 15kHz or as other examples I've heard of K67 capsules without any de-emphasis. Hey, I don't even like overly bright microphones.
:

 

[Studio Mollan]

I ask because I really liked the D67 in Ben's shootout. In this particular case I liked it better than the original U67.
I did notice some extra air in the D67, which I reported in my reply to Ben's post. But it didn't sound as +10dB @ 15kHz or as other examples I've heard of K67 capsules without any de-emphasis. Hey, I don't even like overly bright microphones.
:

I'm also not sure if I like the t67 with the feedback filter but I will try it out. The comparison I did earlier was between the ami without feedback and correctly set up IOaudio transformer. They the dif was ca 6,5db from 1500Hz. What the difference will e with a correctly wired t67 is yet to be discovered. I'll do some shoot outs ASAP but listening to speech in headphones gave me the feeling that the ami is still brighter than IOaudio. Correctly wired the t67 was duller but heavily saturated in the HF. Very present.  Still not confirmed but clips will be posted soon. Speech alone is not a good microphone test in my words. Acoustic guitar and drums are better to get the whole bandwidth and saturation/distortion. 

 

[poctop]

Swapping all three windings will give you the exact same setup as not swapping any.
Swapping the feedback only, with respect to the primary, is the solution that makes sense.
Only swap the secondary (with respect to the primary) if the mic output is out of phase with the sound source - i.e. compare to a known good mic.

i definitively agree with you on this but i am not 100% sure this configuration would not introduce phase shift or other diminishing effect on the demphasis functionnality that i could not confirmed yet.
beeing at swapping the wire, swapping the 3 pair will make sure it will work as intended since the feeback winding is not symetrical. but the final judge is your ear , as stated by micaddict he preffered the non-deempahsis version of it over the real U67  ,  this can still be seen as an extra functionnality or not ,
I will leave this to your discretion but not beeing able to confirm for sure that they can be issue with this only swap i can only recommend to everyone to swap the 3 pair
and if they prefered the currently configured version over the one with the extra demphasis one. then the bright switch can come into play or not.

And the jury is still out on the AMI transformer. It could be that not all the transformers are wound the same way. Some may work as original.
Best to scope out your transformer to verify how it is built.

I am 100% convinced that all the AMI T67 are made the same way.

Best,
Dan,

 

[poctop]

I'll do some shoot outs ASAP but listening to speech in headphones gave me the feeling that the ami is still brighter than IOaudio. Correctly wired the t67 was duller but heavily saturated in the HF. Very present.  Still not confirmed but clips will be posted soon. Speech alone is not a good microphone test in my words. Acoustic guitar and drums are better to get the whole bandwidth and saturation/distortion. 

Absolutely 

 

[poctop]

I have tried to Reach out as many member as possible with the mailing list but some of the contact are expired but here it is again ,

Hi All,

This is a message for all member of the vintage microphone group mailing list , to warn about an errata regarding the connection of the AMI T67 transformer feedback winding through the main mic PCB. It has been identified that the feedback winding is not working properly since an error in the connection to the microphone PCB. The result of this winding being connected backward will affect the de-emphasis portion of the circuit that permits to tame down some high frequency in the response of the microphone.
Don’t worry as this is a simple fix to perform.  As per the builder that have used the IOaudio transformer the connection is correct. This only applies to the use of the AMI T67 transformer in the D-U67 Build.

I would like to ask you  to consult this thread here from page 37 to 41 for the explanation of the quick fix.

I would like to Thank specially member dmp and all other member that helped for pointing this out.

http://groupdiy.com/index.php?topic=50021.720
(Page 37 to 41)

I am really Sorry for the inconvenience and I thank you all  in advance for your cooperation on this matter.

Please let me know if you have any questions regarding this matter.

Best Regards,
Dany ,
http://www.vintagemicrophonepcbkit.com

 

[poctop]

Important AMI T67 Errata

applies to D-M269c and D-U67 with AMI T67 transformer only

Hi All, with the help of  fellow member I have been able to have some testing done about the proper correction for the de-emphasis to work correctly,

it has been found that swapping only 5-12 from the mic pcb make a very sublte difference hence to permits the de-emphasis to work 100% correct,

it is imperative that you swap pad 5-12,  pad 7-10 and pad 1-4 from the mic pcb as the connection have been mistakenly mirrrored.


so the complete 100% fix is
swap 5-12 , 7-10 1-4 pad on the mic PcB,  this will correct for all winding polarity including feedback winding error and correct for a Full de-emphasis.
they all are adjacent pad so it should be pretty easy to correct.


For any Future Build or for the summary of the correction here is the wiring guide for the transformer to the mic pcb ,
this wiring guide ensure all the polarity and connection are as intended at the first place.

From transformer board to mic PCB

Pad 5 ----->  mic pcb pad T1212
Pad 12 -------> mic pcb pad T55
Pad 1 --------> mic pcb pad T44
Pad 4 --------> mic pcb pad T11
Pad 7 --------> mic pcb pad T1010
Pad 10 ------> mic pcb Pad T77


here is some sample before and after the complete fix. Thanks To Dan for the samples.


with wiring error
https://dl.dropboxusercontent.com/u/43869772/U67/Feedback%20winding%20Correction/Orginal.wav

With wiring correction  WoW
https://cdn.groupbuilder.com/groupdiy/u/39511/58d0281994117.wav

Remember that there is an errata on the polarity for the D-67 all you have to do to fix it is reverse pin 2 and pin 3 up in the power supply xlr connector and you will be ready to rock,

PS: for those of you who had the mic output polarity error this will fix this at the same time so i you have reversed xlr pin 2-3 to previously correct for this in the psu please account for that as well as this errata will correct both at the same time.

Thanks For you patience and cooperation and all member helping out resolving this isssues
Best,
Dan.

 

[JessJackson]

Thanks Dani,

Makes complete sense as i was getting reversed phase also. Going to try this out now and put the mic back up today with senheiser / Neumann authentic capsule out of my u87ai.

 

[poctop]

Thanks Dani,

Makes complete sense as i was getting reversed phase also. Going to try this out now and put the mic back up today with senheiser / Neumann authentic capsule out of my u87ai.

Awesome , Cant wait for your verdict,
Best,
DAN,

 

[DeathToneM@]

Just done the rewire for AMI transformer and it's made all the difference.. The mic sounded ok before... But now it has the weight I was expecting from a u67. Top end now sounds perfect!
Thx. M@

 

[micaddict]

Now that this is settled, it would be nice to have some new A/Bs between the AMI and ioaudio tranny in the D67. For sound that is.
Any chance this could happen? E.g. two members getting together somehow. Both mics should have the "same" capsule at least.
Or Dany, will you be building two anywhere in the near future?

 

[saint gillis]

Just done the rewire for AMI transformer and it's made all the difference.. The mic sounded ok before... But now it has the weight I was expecting from a u67. Top end now sounds perfect!
Thx. M@

  Totally agree, seems far better!